VGO is a hydrocarbon fraction that may be converted into higher value hydrocarbon fractions such as diesel fuel, jet fuel, naphtha, gasoline, and other lower boiling fractions in refining processes such as hydrocracking and fluid catalytic cracking (FCC). However, VGO feed streams having higher amounts of nitrogen are more difficult to convert. For example, the degree of conversion, product yields, catalyst deactivation, and/or ability to meet product quality specifications may be adversely affected by the nitrogen content of the feed stream. It is known to reduce the nitrogen content of VGO by catalytic hydrogenation reactions such as in a hydrotreating process unit.
Similar issues are involved in the processing of diesel fuel. Diesel fuel contains sulfur-containing molecules that are well known pollutants. Therefore, there is an ever increasing need to provide diesel fuels that have ultra low sulfur content. A typical way of removing sulfur from diesel fuel is by catalytic hydrodesulfurization (HDS). It is, however, becoming more difficult to catalytically hydrodesulfurize diesel fuels to the lower level of sulfur now required. Since nitrogen content interferes with the effective removal of sulfur, it is necessary to remove nitrogen prior to removing the sulfur.
Various processes using ionic liquids to remove sulfur and nitrogen compounds from hydrocarbon fractions are also known. U.S. Pat. No. 7,001,504 B2 discloses a process for the removal of organosulfur compounds from hydrocarbon materials which includes contacting an ionic liquid with a hydrocarbon material to extract sulfur containing compounds into the ionic liquid. U.S. Pat. No. 7,553,406 B2 discloses a process for removing polarizable impurities from hydrocarbons and mixtures of hydrocarbons using ionic liquids as an extraction medium. U.S. Pat. No. 7,553,406 B2 also discloses that different ionic liquids show different extractive properties for different polarizable compounds.
There remains a need in the art for improved processes that enable the removal of compounds comprising nitrogen from vacuum gas oil (VGO) and diesel fuels as well as from other fuels.
Caprolactamium is an intermediate in the manufacture of caprolactam which in turn is used in the production of engineering polymers such as polyamide 6. Since millions of tons of caprolactam are used per year, there are correspondingly large amounts of the caprolactamium ionic liquid that are produced. While this ionic liquid has been known for many years, it is shown here to be effective in treatment of fuels, such as diesel fuel and vacuum gas oil.